This invention is primarily for use with mineral insulated ("MI") cables. Such cables have an outer metal sheath, generally made from a copper tube. One or more conductors are located at a central region of the cross-section of the interior of the copper tube, and these conductors are insulated from the metal sheath and from each other by mineral insulation such as magnesium oxide which fills the interior of the copper tube and which spaces the conductors from the inside wall of the tube and also spaces the conductors from one another when the cable contains more than one conductor.
At terminations of such cables, the end portion of the cable is inserted into a gland assembly; and is secured to the gland assembly by a compression ring which surrounds the circumference of the cable. The compression ring is wedged against the outside of the cable sheath, and the inner end of the cable extends into a chamber in the gland assembly which provides a space for a "pot" threaded over the end of the cable sheath with the conductor of the cable extending beyond the gland and pot.
The purpose of the pot is to hold a sealant in contact with the end of the cable sheath and across the exposed surface of the mineral insulation before the cable is installed in a circuit.
Gland assemblies for mineral insulated cables were made in different sizes for cables of different size.
This invention provides a gland assembly using the same size gland body and lock nut for any cable within a range of different cable sizes. The lock nut clamps a compression ring against the outside of the cable to secure the gland assembly to the cable; and these compression rings are all of the same outside diameter, but each compression ring must have an inside diameter corresponding to the diameter of the cable. Inventory is substantially reduced with resulting savings in expense to suppliers of the gland assemblies.
Lock nuts used in gland assemblies of the prior art screwed over the gland body and forced compression rings into contact with the outside of the cable. When the lock nuts were over-tightened, the compression ring would sometimes fracture the sheath of the cable. The present invention has a surface against which the lock nut bottoms to prevent over-tightening and resulting excess pressure on the compression ring.
It is a feature of the invention that the compression rings are annealed and made of metal which is capable of some cold flow when securing the gland assembly of this invention to a mineral insulated cable.
Other objects, features and advantages of the invention will appear or be pointed out as the description proceeds.